Composite coil spring

ABSTRACT

A composite coil spring includes a coil body that extends along a coiled axis. The coil body includes a core and a plurality of fiber layers impregnated with a polymer material. The plurality of fiber layers are arranged around the core at different radial distances from the coiled axis. Each of the plurality of fiber layers extends around the coiled axis at an oblique fiber angle to the coiled axis. Each of the plurality of fiber layers includes a number of fibers that is a product of a common base number of fibers multiplied by a positive non-zero integer from a set of positive non-zero integers. The positive non-zero integer of at least one of the plurality of fiber layers is different from the positive non-zero integer of at least one other of the plurality of fiber layers.

BACKGROUND

This disclosure relates to composite coil springs that may be used invehicle suspension systems.

Coil springs are known and used in a variety of different applications,such as vehicle suspension systems. A typical coil spring is fabricatedof a steel material in order to provide the desired mechanicalproperties and durability that is required for such applications. As analternative, composite coil springs are desired as a replacement forsteel coil springs due to weight savings. However, although compositecoil springs may be known and used in some applications, it is oftendifficult to design such composite coil springs with the desiredmechanical properties for a given application, and then to fabricate thecomposite coil spring economically.

SUMMARY

A composite coil spring includes a coil body that extends along a coiledaxis. The coil body includes a core and a plurality of fiber layersimpregnated with a polymer material. The plurality of fiber layers arearranged around the core at different radial distances from the coiledaxis. Each of the plurality of fiber layers extends around the coiledaxis at an oblique fiber angle to the coiled axis. Each of the pluralityof fiber layers includes a number of fibers that is a product of acommon base number of fibers multiplied by a positive non-zero integerfrom a set of positive non-zero integers. The positive non-zero integerof at least one of the plurality of fiber layers is different from thepositive non-zero integer of at least one other of the plurality offiber layers.

In other aspect, a composite coil spring includes a coil body thatextends along a coiled axis. The coil body includes a fibrous core and aplurality of fiber layers impregnated with a polymer material. Theplurality of fiber layers are arranged around the fibrous core atdifferent radial distances from the coiled axis. Each of the pluralityof fiber layers extends around the coiled axis at an oblique angle tothe coiled axis. Each of the plurality of fiber layers and the fibrouscore include a number of fibers that is a product of a common basenumber of fibers multiplied by a positive non-zero integer from a set ofpositive non-zero integers. The positive non-zero integer of at leastone of the plurality of fiber layers is different from the positivenon-zero integer of the fibrous core.

In a further aspect, a method of fabricating the composite coil springincludes forming the coil body as set forth above.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of the present disclosure willbecome apparent to those skilled in the art from the following detaileddescription. The drawings that accompany the detailed description can bebriefly described as follows.

FIG. 1 shows a composite coil spring.

FIG. 2 shows a cross-section of the coil spring taken perpendicularly toa coiled axis of the coil spring of FIG. 1.

FIG. 3 shows a portion of a fiber layer of the composite coil spring ofFIG. 1.

FIG. 4 shows alternating fiber orientations of fiber layers of thecomposite coil spring of FIG. 1.

FIG. 5 shows an example fibrous core for a composite spring coil.

FIG. 6 shows an example solid core for a composite spring coil.

FIG. 7 shows an example hollow tube core for a composite spring coil.

FIG. 8 shows an example filled tube core for a composite spring coil.

DETAILED DESCRIPTION

FIG. 1 shows an example composite coil spring 20 that may be used in asuspension system of a vehicle, for example. It is to be understood,however, that the composite coil spring 20 is not limited to such uses.The composite coil spring 20 may be helical or alternatively have adifferent coil shape. In this disclosure, a “coil” or variations thereofmeans a body that curves continuously around a fixed linear axis, suchas axis A in FIG. 1. As will be appreciated, the composite coil spring20 is strong and lightweight and therefore provides a weight reductionfor the replacement of metallic coil springs in vehicles or otherapplications, which can improve fuel mileage.

The composite coil spring 20 includes a coil body 22 that extends alonga coiled axis 24 between terminal ends 26/28. Referring also to across-section of the coil body 22 shown in FIG. 2 and a portion of thecomposite coil spring 20 shown in FIG. 3, the coil body 22 includes apolymer material 30 and a plurality of fiber layers 32 impregnated withthe polymer material 30. For example, the polymer material 30 can beepoxy or polyester. Alternatively, the polymer material can be adifferent composition of organic polymer than epoxy or polyester. A“layer” has a uniform radial thickness around the entire layercircumference.

Each of the fiber layers 32 includes a plurality of fibers 34 that arearranged at an oblique fiber angle α (alpha) to the coiled axis 24. Forexample, the fibers 34 are or include metallic fibers, ceramic fibers,organic fibers or combinations thereof. In further examples, the fibers34 are glass fibers, carbon fibers, aramid fibers or combinationsthereof. For purposes of description, the fibers 34 of the fiber layers32 are not shown in FIG. 2.

The fibers 34 of each of the fiber layers 32 extend around the coiledaxis 24 at the selected oblique fiber angle α. In one example, theoblique fiber angle α is +/−20-54° to provide the coil body 22 with ahigh degree of strength. The fiber layers 32 may alternate in fiberorientation such that the oblique fiber angle α of any one of the fiberlayers 32 is also oblique to one or two directly neighboring ones of thefiber layers 32 (FIG. 4) at each location along the coiled axis 24.

The fiber layers 32 are arranged at different radial distances, as shownat 36, from the coiled axis 24. In this disclosure, the radial distances36 are the distances between the coiled axis 24 and the radially innersurface of the fiber layers 32.

As shown in FIG. 2, the plurality of fiber layers 32 includes fiberlayers 32 a-f. Fiber layer 32 a is an innermost layer with regard toradial distance from the coiled axis 24 and fiber layer 32 f is anoutermost layer with regard to radial distance from the coiled axis 24.As used in this disclosure, the terms “innermost” and “outermost” meanthat there are no other fiber layers located radially inwards orradially outwards of, respectively, of the innermost fiber layer 32 aand the outermost fiber layer 32 f.

In this example, the fiber layers 32 are wound around a core 38. Thecore 38 can be a fibrous core 138 impregnated with the polymer 30 (FIG.5). The fibers 34 of the fibrous core 138 can extend substantiallyparallel to the coiled axis 24, within +/−20°. In another alternative,the core 38 can be a solid, non-fibrous core 238 (FIG. 6) that ispolymeric or metallic. In other alternatives, the core 38 can be ahollow tube 338 (FIG. 7) or a tube 438 (FIG. 8) that has an interiorcavity 450 that includes a filler material 452. The filler material 452can be different in composition from the material of the tube 448, suchas two different polymer compositions, metallic compositions orcombinations. The material and diameter of the core 38 can be selectedsuch that the core 38 is flexible to allow formation of the desired coilshape. In any of the above examples, the core 38 can be or can include ashape memory material that changes shape in response to changes intemperature relative to a temperature threshold, to aid in formation ofthe coil shape.

Each of the fiber layers 32 and, optionally, the fibrous core 138includes a number of the fibers 34 that is a product of a common basenumber of fibers multiplied by a positive non-zero integer selected froma set of positive non-zero integers. The common base number is apredetermined number that is equal for each of the fiber layers 32 andthe fibrous core 138. The positive non-zero integer of at least one ofthe fiber layers 32 is different from the positive non-zero integer ofthe fibrous core 38 and can also be different from at least one other ofthe fiber layers 32. Using the number of fibers 34 that is a product ofthe common base number of fibers multiplied by a positive non-zerointeger selected from the set of positive non-zero integers facilitatesmanufacturing and also provides a desirable strength profile.

In a further example, the fibrous core 138 and the outermost fiber layer32 f (multiple second fiber layers) have equal positive non-zerointegers. The fiber layers 32 a-e are intermediate layers (multiplefirst fiber layers) that are arranged radially between the fibrous core138 and the outermost fiber layer 32 f. In this example, theintermediate fiber layers 32 a-e have equal positive non-zero integersand these integers are non-equal to the integers of the fibrous core 138and the outermost fiber layer 32 f. That is, at least two of the fiberlayers 32 have different positive non-zero integers and at least one ofthe fiber layers 32 has a different positive non-zero integer than thefibrous core 138. In this example, the positive non-zero integer of theintermediate fiber layers 32 a-e is less than the positive non-zerointeger of the fibrous core 138 and the outermost fiber layer 32 f,which can be equal.

In a further example, the intermediate fiber layers 32 a-e each have anumber of fibers N1 and the fibrous core and the outermost fiber layer32 f each have a number of fibers N2 that is different from the numberof fibers N1 by a multiplier factor. In a further example, the positivemultiplier factor is 2-20.

As a further example, the number of fibers 34 in any one of the fiberlayers 32 and the fibrous core 138 corresponds to the number of fibers34 in one or more fiber rovings that are used to fabricate the fiberlayers 32 and fibrous core 138 of the coil body 22. For example, asingle fiber roving may have 2,000 individual fibers and 11 rovings thatestablish the common base number of fibers, which in this example wouldbe 22,000 fibers. Thus, the actual number of fibers 34 in any one of thefiber layers 32 and fibrous core 138 would be 22,000 fibers multipliedby the selected positive non-zero integer for that individual fiberlayer 32. For example, the set of positive non-zero integers is between1 and 20. It is to be understood, however, that the number of fibers 34per roving and the number of rovings used to determine the common basenumber of fibers can be varied. In a further example, between 4 and 60rovings may be used, with either 2,000 or 4,000 fibers per roving.

It is to be further understood that the number of fibers 34 in any oneof the fiber layers 32 or the fibrous core 138 may practically varysomewhat because a small number of fibers 34 may break duringfabrication and/or rovings may vary from a nominal fiber count. Thus, inexamples where the numbers of fibers 34 in fiber layers 32 are equal, orthe numbers of fibers 34 in any of the fiber layers 32 and in thefibrous core 138 are equal, the equivalence can be based upon thenominal numbers of fibers. Similarly, where the numbers of fibers 34 infiber layers 32 are different, or the numbers of fibers 34 in any of thefiber layers 32 and in the fibrous core 138 are different, thedifference can be based upon the nominal numbers of fibers.

In the above example where there are 2,000 fibers per roving and 11rovings to establish the common base number of fibers, the positivenon-zero integer of the intermediate layers 32 a-e is 1, and thepositive non-zero integers of each of the fibrous core 138 and theoutermost fiber layer 32 f is 3. Thus, the positive non-zero integers ofat least two of the fiber layers 32 differ by at least 2, and thepositive non-zero integer multiplier factor is 3.

A method of fabricating the composite coil spring 20 includes formingthe coil body 22 as described above. For example, for a given fiberlayer 32 or the optional fibrous core 138, an appropriate number ofspools or fiber rovings corresponding to the selected positive non-zerointeger for that fiber layer 32 or the fibrous core 138 provide thefibers 34 through a guide device and a reservoir of the polymer resinmaterial to impregnate the fibers 34. The impregnated fibers are thenwound around the core 38 using winding equipment. This process isrepeated for each of the fiber layers 32 until a desired number of fiberlayers 32 are wound.

The resulting resin-impregnated fiber structure is then removed from thewinding equipment. The structure is arranged into a coil groove of amandrel. The coil groove corresponds to the desired end shape of thecomposite coil spring 20. The mandrel and structure are then heated in afurnace to cure the resin and thereby form the permanent shape of thecomposite coil spring 20. The heating temperature and time depend uponthe type of polymer material selected and, given this description, oneof ordinary skill in the art will be able to determine a suitableheating temperature and time to meet their particular needs. The mandrelis then removed by mechanical or other means, leaving the finished ornear finished composite coil spring 20.

Although a combination of features is shown in the illustrated examples,not all of them need to be combined to realize the benefits of variousembodiments of this disclosure. In other words, a system designedaccording to an embodiment of this disclosure will not necessarilyinclude all of the features shown in any one of the Figures or all ofthe portions schematically shown in the Figures. Moreover, selectedfeatures of one example embodiment may be combined with selectedfeatures of other example embodiments.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this disclosure. The scope of legal protection given tothis disclosure can only be determined by studying the following claims.

What is claimed is:
 1. A composite coil spring comprising: a coil bodyextending along a coiled axis, the coil body including a core and aplurality of fiber layers impregnated with a polymer material, theplurality of fiber layers being arranged around the core at differentradial distances from the coiled axis, each of the plurality of fiberlayers extending around the coiled axis at an oblique fiber angle to thecoiled axis, each of the plurality of fiber layers including a number offibers that is a product of a common base number of fibers multiplied bya positive non-zero integer from a set of positive non-zero integers,and the positive non-zero integer of at least one of the plurality offiber layers is different from the positive non-zero integer of at leastone other of the plurality of fiber layers.
 2. The composite coil springas recited in claim 1, wherein the set of positive non-zero integers is1-20.
 3. The composite coil spring as recited in claim 1, wherein theoblique angle is +/−20-54°.
 4. The composite coil spring as recited inclaim 1, wherein, relative to the coiled axis, an innermost layer of theplurality of fiber layers and an outermost layer of the plurality offiber layers have equal positive non-zero integers.
 5. The compositecoil spring as recited in claim 1, wherein the core is a fibrous coreand intermediate fiber layers of the plurality of fiber layers haveequal positive non-zero integers, the intermediate fiber layers beingarranged, relative to the coiled axis, between the fibrous core and anoutermost fiber layer of the plurality of fiber layers.
 6. The compositecoil spring as recited in claim 1, wherein the positive non-zerointegers of at least two of the plurality of fiber layers that aredifferent, differ by at least
 1. 7. The composite coil spring as recitedin claim 1, wherein the oblique fiber angle of each of the plurality offiber layers is also oblique to at least one directly neighboring one ofthe plurality of fiber layers.
 8. The composite coil spring as recitedin claim 1, wherein the polymer material includes epoxy.
 9. Thecomposite coil spring as recited in claim 1, wherein the polymermaterial includes polyester.
 10. The composite coil spring as recited inclaim 1, wherein the plurality of fiber layers are selected from thegroup consisting of glass fibers, carbon fibers, aramid fibers andcombinations thereof.
 11. The composite coil spring as recited in claim1, wherein the plurality of fiber layers are selected from the groupconsisting of metallic fibers, ceramic fibers, organic fibers andcombinations thereof.
 12. The composite coil spring as recited in claim1, wherein the core is a fibrous core and includes a number of fibersthat is a product of the common base number of fibers multiplied by thepositive non-zero integer from the set of positive non-zero integers,and the positive non-zero integer of at least one of the plurality offiber layers is different from the positive non-zero integer of thefibrous core.
 13. The composite coil spring as recited in claim 1,wherein the core is a solid core.
 14. The composite coil spring asrecited in claim 13, wherein the solid core is polymeric.
 15. Thecomposite coil spring as recited in claim 13, wherein the solid core ismetallic.
 16. The composite coil spring as recited in claim 1, whereinthe core includes a shape memory material.
 17. The composite coil springas recited in claim 1, wherein the core is a hollow tube.
 18. Thecomposite coil spring as recited in claim 1, wherein the core is a tubedefining an interior cavity, and the interior cavity includes a fillermaterial therein.
 19. A composite coil spring comprising: a coil bodyextending along a coiled axis, the coil body including a fibrous coreand a plurality of fiber layers impregnated with a polymer material, theplurality of fiber layers being arranged around the fibrous core atdifferent radial distances from the coiled axis, each of the pluralityof fiber layers extending around the coiled axis at an oblique angle tothe coiled axis, each of the plurality of fiber layers and the fibrouscore including a number of fibers that is a product of a common basenumber of fibers multiplied by a positive non-zero integer from a set ofpositive non-zero integers, and the positive non-zero integer of atleast one of the plurality of fiber layers is different from thepositive non-zero integer of the fibrous core.
 20. The composite coilspring as recited in claim 19, wherein the plurality of fiber layersinclude at least one first fiber layer and at least one second fiberlayer, the first fiber layer having a number of fibers N1 and the secondfiber layer having a number of fibers N2 that is different from thenumber of fibers N1.
 21. The composite coil spring as recited in claim20, wherein the number of fibers N2 is different from the number offibers N1 by a positive multiplier factor of 2-20.
 22. The compositecoil spring as recited in claim 20, wherein, relative to the coiledaxis, the second fiber layer is an outermost layer and the first fiberlayer is an intermediate fiber layer arranged between the outermostlayer and the fibrous core.
 23. The composite coil spring as recited inclaim 19, wherein the oblique fiber angle of each of the plurality offiber layers is also oblique to at least one directly neighboring one ofthe plurality of fiber layers.
 24. The composite coil spring as recitedin claim 19, wherein the oblique angle is +/−20-54°.
 25. A method offabricating a composite coil spring, the method comprising: forming acoil body along a coiled axis from a core and a plurality of fiberlayers impregnated with a polymer material, the plurality of fiberlayers being arranged around the core at different radial distances fromthe coiled axis, each of the plurality of fiber layers extending aroundthe coiled axis at an oblique fiber angle to the coiled axis, each ofthe plurality of fiber layers including a number of fibers that is aproduct of a common base number of fibers multiplied by a positivenon-zero integer from a set of positive non-zero integers, and thepositive non-zero integers of at least one of the plurality of fiberlayers is different from the positive non-zero integer of at least oneother of the plurality of fiber layers.